Communications apparatus and methods for adaptive signal processing based on mobility characteristics

ABSTRACT

Information represented by a signal generated in a communications medium by a first entity is recovered by receiving the signal from the communications medium at a second entity, determining a mobility characteristic for communications between the first entity and the second entity, and adaptively estimating the information from the received signal based on the determined mobility characteristic. The mobility characteristic may be received from the first entity at the second entity, and the information represented by the received signal may be adaptively estimated based on the received mobility characteristic. According to an embodiment of the invention, the mobility characteristic is a cell type identifier which is communicated from a base station to a mobile terminal, the mobile terminal adaptively estimating information from a signal received from the base station based on the communicated cell type identifier. A number of signal processing functions may be adaptively performed, including adaptive demodulation, adaptive channel estimation/interpolation, adaptive equalization, adaptive channel tracking, and adaptive combining of received signals.

This is a continuation application of application Ser. No. 08/908,088,filed Aug. 8, 1997.

FIELD OF THE INVENTION

The present invention relates to communications systems and methods, inparticular, to systems and methods for recovering information fromsignals generated in a communications medium.

BACKGROUND OF THE INVENTION

Radiotelephone systems are commonly employed to provide voice and datacommunications to a plurality of mobile units or subscribers. Forexample, analog cellular radiotelephone systems, such as designatedAMPS, ETACS, NMT-450, and NMT-900, have been deployed successfullythroughout the world. More recently, digital cellular radiotelephonesystems such as designated IS-54B in North America and the pan-EuropeanGSM system have been introduced. These systems, and others, aredescribed, for example, in the book titled Cellular Radio Systems byBalston, et al., published by Artech House, Norwood, Mass, 1993.

As illustrated in FIG. 1, a conventional cellular communication system20 includes one or more mobile terminals 10 which can communicate withone or more base stations 20 serving cells 30. The base stations 20 areconnected to a mobile telephone switching office (MTSO) 40, which may inturn be connected to a public switched telephone network 50. Althoughonly two cells 20 are shown in FIG. 1, a typical cellular network mayinclude hundreds of base stations, thousands of mobile terminals andmore than one MTSO. Each cell will have allocated to it one or morededicated control channels and one or more voice channels. Through thiscellular infrastructure, a communication link may be effected betweentwo mobile terminals 10, or between a mobile terminal 10 and a landlinetelephone 60, with a base station 20 typically functioning as a relaystation for data and voice information.

Components of a radio communications channel connecting a mobileterminal 10 and abase station 20 which can affect communications betweenthe terminal 10 and the base station 20 include the communicationsmedium, i.e., the atmospheric signal path across which radiocommunications signals are transmitted, which may introduce fading andinterference into the radio communications signals. The fading mayinclude long-term fading due to variations in terrain along the signalpropagation path, as well as short-term multipath fading due toreflections from features such as buildings which cause fluctuations inreceived signal strength and other distortions at a receiving station.Mobile terrestrial radiotelephone communications are particularlysusceptible to short-term multipath fading because the signal pathwaystend to be close to the ground. Other elements which may have an effecton communications include transmitting and receiving components commonlyfound in base stations and mobile terminals, such as transmitters,receivers and antennas.

Various signal estimation techniques are conventionally employed to dealwith signal degradation on a channel, including diversity reception,signal coding, and specialized demodulation techniques which produceestimates of a channel transfer characteristic. Diversity receptiontechniques included spatial diversity reception using multiple spacedapart receiving antennas, and polarization diversity reception usingmultiple antennas designed to accept electromagnetic signals havingparticular polarizations. As signals from diverse paths typicallyexhibit uncorrelated fading, they may be combined in the receiver toprovide a more accurate estimate of information from a received signal.Signal coding schemes typically employ redundancy to enhance theaccuracy of an estimate produced from a received signal, while channelestimation techniques such as pilot tone or symbol assisted modulationand demodulation can provide improved knowledge of a transfercharacteristic for the channel to aid in estimating information from areceived signal.

Despite the theoretical advantages of these estimation techniques, theymay provide less than optimal communication under various propagationconditions encountered in a typical cellular communications system.Diversity reception may not provide sufficient gain because oflimitations on antenna size, orientation, and placement, and may beineffective or unnecessary at particular speeds or other conditions.Coding schemes may entail an undesirable computational burden, whileparameters used in estimating the channel may not be optimal for allmobile terminal speeds and under all delay spread conditions.

SUMMARY OF THE INVENTION

In light of the foregoing, it is an object of the present invention toprovide communications apparatus and methods which can provide improvedsignal estimation.

It is another object of the present invention to provide cellularcommunications apparatus and methods which can provide more optimalsignal estimation under differing conditions of delay spread andterminal speed.

These and other objects, features and advantages are provided accordingto the present invention by communications apparatus and methods inwhich information is recovered at one entity, e.g., a mobile terminal,from a signal generated in a communications medium by another entity,e.g., a cellular base station, by adaptively estimating the informationfrom the signal based on a mobility characteristic which characterizescommunications between the entities. The process can be bidirectional,i.e., adaptive estimation of received signal may be performed at eitherend of a communications channel. The mobility characteristic maycharacterize mobility properties of the entities which affect signalpropagation between the entities, such as relative speeds of theentities with respect to one another, range between the entities, andthe like. According to one embodiment, the mobility characteristicincludes a cell type identifier which characterizes mobility of mobileterminals with respect to a base station, e.g., an identifier whichidentifies a cell served by the base station as a highway macrocell, anurban macrocell, a microcell or the like, and which bears a correlationto aggregate speed and range properties for terminals typically foundwithin the cell. The cell type identifier may be broadcast to mobileterminals from the base station over, for example, a broadcast controlchannel, and the mobile terminals can adaptively estimate informationfrom signals received from the base station based on the broadcast celltype identifier. For example, the mobile terminal may store varioussignal processing elements such as channel estimators, channelinterpolation filters, channel trackers, and the like, as well asvarious parameters for such elements, and may apply these selectedelements and parameters to a signal received from a base station basedon a cell type identifier received from the station. Accordingly, moreoptimal signal estimation can be achieved by tailoring signal processingto the mobility characteristic.

In particular, according to the present invention, a communicationssystem for communicating across a communications medium includes a firstentity including means for generating a signal in the communicationsmedium, the signal representing information, and a second entityincluding signal receiving means, responsive to the communicationsmedium, for receiving a signal from the communications medium. Thesecond also includes means for determining a mobility characteristic forcommunications between the first entity and the second entity, as wellas adaptive estimating means, responsive to the signal receiving means,for adaptively estimating the information from the received signal basedon the determined mobility characteristic.

According to one aspect of the present invention, the first entityfurther includes means for transmitting a mobility characteristic, andthe means for determining a mobility characteristic includes means forreceiving the transmitted mobility characteristic. The adaptiveestimating means may include means for adaptively estimating theinformation based on the received mobility characteristic. The adaptiveestimating means may include a number of different adaptive signalprocessing apparatus, including means for adaptively demodulating thereceived signal based on the determine mobility characteristic, meansfor adaptively estimating a characteristic for a channel connecting thefirst and second entities based on the determined mobilitycharacteristic, means for selecting an interpolation filter based on thedetermined mobility characteristic, means for adaptively equalizing thereceived signal based on the determined mobility characteristic, meansfor adaptively tracking a channel connecting the base station and themobile terminal based on the determined mobility characteristic, andmeans for adaptively combining a plurality of received signals based onthe determined mobility characteristic.

According to an embodiment of the present invention, a cellularcommunications system includes a base station, a mobile terminal, andmeans for communicating a mobility characteristic associated withcommunications of the base station and the terminal, between the basestation and the terminal. A first one of the base station and the mobileterminal may include means for generating a signal in a communicationsmedium, the generated signal representing information. A second one ofthe base station and the mobile terminal may include signal receivingmeans, responsive to the communications medium, for receiving thegenerated signal from the communications medium, and adaptive estimatingmeans, responsive to the signal receiving means, for adaptivelyestimating the information from the received signal based on thereceived mobility characteristic. The means for communicating a mobilitycharacteristic may include means for broadcasting a cell type identifierfrom the base station, for example, over a broadcast control channel.The means for communicating a mobility characteristic may also includemeans for communicating the mobility characteristic on a channelspecific to the mobile terminal, such as an access grant channel or afast associated control channel.

According to another aspect of the present invention, a communicationsterminal includes signal receiving means, responsive to a communicationsmedium, for receiving a signal from the communications medium. Means areprovided for determining a mobility characteristic associated with thecommunications medium, and adaptive estimating means are responsive tothe signal receiving means and the mobility characteristic determiningmeans, for adaptively estimating information from the received signalbased on the determined mobility characteristic. The means fordetermining a mobility characteristic may include means for receiving amobility characteristic, and the adaptive estimating means mayadaptively estimate the information based on the received mobilitycharacteristic.

According to method aspects of the present invention, informationrepresented by a signal generated in a communications medium by a firstentity is recovered by receiving the signal from the communicationsmedium at a second entity, determining a mobility characteristic forcommunications between the first entity and the second entity, andadaptively estimating the information from the received signal based onthe determined mobility characteristic. The mobility characteristic maybe received from the first entity at the second entity, and theinformation represented by the received signal may be adaptivelyestimated based on the received mobility characteristic. A number ofsignal processing functions may be adaptively performed, includingadaptive demodulation, adaptive channel estimation/interpolation,adaptive equalization, adaptive channel tracking, and adaptive combiningof received signals. Improved communications may thereby be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects and advantages of the present invention having beenstated, others will be more fully understood from the detaileddescription that follows and by reference to the accompanying drawingsin which:

FIG. 1 is a schematic diagram illustrating a conventional cellularcommunications system;

FIGS. 2-3 are schematic diagrams illustrating embodiments of a cellularcommunications system according to the present invention;

FIG. 4 is a schematic diagrams illustrating use of cell type identifierin embodiments of a cellular communications system according to thepresent invention;

FIG. 5 is a schematic diagram illustrating adaptive channel estimationaccording to the present invention;

FIG. 6 is a schematic diagram illustrating adaptive demodulationaccording to the present invention;

FIG. 7 is a schematic diagram illustrating adaptive signal combiningaccording to the present invention; and

FIG. 8 is a flowchart illustration of operations for recoveringinformation from a signal according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, like numbers refer to like elements throughout.

For purposes of the discussion herein, “estimation of information” froma signal refers generally to those operations commonly known as “signalestimation” or “signal processing” in which information is extractedfrom an electromagnetic signal used to represent the information,including, but not limited to, operations such as demodulation,filtering, sampling, equalizing and the like. In addition, “mobilitycharacteristic” as referred to herein includes information relating tospatio-temporal relationships which may impact on communications betweenentities of a communications system. For example, in a cellularcommunications system in which mobile terminals communicate with basestations which serve geographical cells, a mobility characteristic mayinclude information relating to spatial-temporal relationships betweenbase stations and mobile terminals, such as speed or range of a specificmobile terminal or typical speed and range characteristics of apopulation of mobile terminals within a cell with respect to a basestation serving the cell. The present invention arises from therealization that due to the effect these mobility characteristics canhave on signal properties, e.g., delay spread, more optimal estimationof information from a signal received from a communications medium,e.g., more optimal signal processing, may be achieved by adaptivelytailoring signal processing architectures and parameters to varyingmobility characteristics.

FIG. 2 provides an illustration of a cellular communication systemaccording to the present invention, including a base station 210 whichincludes means for generating a signal 215 in a communications medium,for example, a transmitter 202 generating a signal through a transmitantenna 204. A mobile terminal 220 includes signal receiving meansincluding, for example, a receive antenna 222, for receiving thegenerated signal 215. The received signal 223 is processed by adaptiveestimating means 224 included in the mobile terminal 220, based on amobility characteristic 227 determined by mobility characteristicdetermining means 226. As illustrated in FIG. 3, the roles of the basestation 210 and the mobile terminal 220 may be reversed, with the basestation 210 including signal receiving means, e.g, a base stationantenna 212 and associated hardware, for receiving a signal 211generated by the mobile terminal 220. Information 215 is adaptivelyestimated from the received signal 213 by adaptive estimating means 214,based on a mobility characteristic 217 determined by mobilitycharacteristic determining means 216 included in the base station 210.

Those skilled in the art will appreciate that signal generating means ofthe base station 210 and the mobile terminal 220 may include, forexample, commonly used communications components such as signalprocessors, coders, modulators, mixers, antennas, filters and the like,and may be implemented using special purpose hardware, software runningon special or general purpose processors, and combinations thereof.Similarly, the signal receiving means described above may include suchcomponents as antennas, cables, waveguides, mixers, filters and thelike. The mobility characteristic determining means 216, 226 and theadaptive estimating means 214, 224 described with respect to FIGS. 2-3may be implemented using special purpose hardware, software running ongeneral purpose processors such as a microprocessor, or combinationsthereof. For example, the mobility characteristic determining means 216,226 may include software running on a microprocessor which determines amobility characteristic for communications between the base station 210and the mobile terminal 220, while a digital signal processing (DSP)chip or application specific integrated circuit (ASIC) may be used toimplement functions of the adaptive estimating means 214, 224, e.g.,various signal processing tasks such as demodulation, channelestimation, and the like.

According to one embodiment of the invention, the mobilitycharacteristic includes a cell type identifier which is communicatedbetween a base station 410 and a mobile terminal 420, as illustrated inFIG. 4. The cell type identifier may be communicated in a number ofways, included by broadcasting the cell type identifier from the basestation 410 over a broadcast control channel 414. The mobile terminal420 may include means for receiving the broadcast cell type identifier424, such as receiver circuitry and associated elements which arecommonly included in mobile terminals. Adaptive estimating means 422,e.g., demodulating circuitry, signal processing circuitry and the like,are responsive to the cell type identifier receiving means 424 forestimating information from a signal, for example, a signal receivedover a traffic channel 512, for estimating information from the receivedsignal based on the received cell type identifier 425.

Tables I and II illustrate exemplary relationships mobility and signalcharacteristics associated with different cell types under the U.S.IS-136 and the European GSM standards, respectively, and desirablesignal processing options for these conditions:

TABLE I Signal Processing Options for IS-136 (and enhanced versions)Signal Cell Type Typical Attributes processing options Highway macrocellHigh delay spread Apply equalization High terminal speed High speedchannel tracking and channel interpolation High/Medium terminal Disablediversity speed reception Urban macrocell Low delay spread Differentialdetection or low-order equalizer (1 tap) Medium terminal speed Mediumspeed channel tracking and channel interpolation Microcell Low delayspread Differential detection or low order equalizer (1 tap) Lowterminal speed Low speed channel tracking and channel interpolation,enable diversity reception Picocell Low delay spread Differentialdetection or low order equalizer Low speed Low speed channel trackingand channel interpolation, enable diversity reception

TABLE II Signal Processing Options for GSM Signal Cell Type TypicalAttributes processing options Highway macrocell High delay spread Highorder equalizer High terminal speed Enable channel tracking Urbanmacrocell Low/Medium delay spread Medium order equalizer (4 taps) Mediumterminal speed Disable channel tracking Microcell Low/medium delayspread Low/medium order equalizer (3-4 taps) Low terminal speed Disablechannel tracking Picocell Low delay spread Low order equalizer (3 taps)Low speed Disable channel tracking Low speed channel interpolation

Those skilled in the art will appreciate that other types of mobilitycharacteristics and techniques for determining mobility characteristicsfor adaptive signal processing fall within the scope of the presentinvention. For example, instead of an indirect measurement of mobilitywhich provides mobility information on a typical population of mobileterminals with respect to a base station, mobile-specific informationsuch as the range and speed of a particular terminal may be determined.This information may also be communicated on a mobile-specific basis,instead of by broadcasting to a population of terminals on a commoncontrol channel. For example, a base station may compute range and speedfor a terminal and transmit the computed information to the terminal onan access grant channel or fast associated control channel, and themobile terminal may use this information to adaptively select from a“bank” of algorithms and/or algorithm parameters to optimally adapt itsprocessing of signals received from the base station. In anotherimplementation, a mobile terminal may include means for determiningspeed and range with respect to a particular base station with which itis communicating, and may use this information to adjust its signalprocessing. A base station could also perform similar computations toadjust its own signal processing.

An aspect of adaptive signal estimation according to the presentinvention is illustrated in FIG. 5. In FIG. 5, an estimate 535 ofsymbols represented by a received signal 505 is produced in an adaptivefashion using a pilot-symbol assisted technique. Sampling means 510produces a sequence of received symbols 515. Pilot symbols 523 areextracted from the sequence 515 by decimating means 520, and are passedto channel estimating means 560 and the channel interpolating means 540.The channel interpolating means 540 interpolate a channel characteristic545 for a channel over which the received signal 505 is received, e.g.,a communications channel which connects a base station and a mobileterminal, using a channel interpolation filter 543 selected byinterpolation filter selecting means 550 according to a mobilitycharacteristic 547. Symbol estimating means 530 estimate the originalsymbol sequence represented by the received signal 505, using theinterpolated channel characteristic 545.

Those skilled in the art will appreciate that the means of FIG. 5 may beimplemented using a variety of commonly-used communications components,including special purpose hardware, software or firmware running on adata processing apparatus or combinations thereof. For example, samplingmeans 510 may include analog-to-digital converters (A/Ds), associatedfilters, and the like. The functions of interpolation filter selectingmeans 550 may, for example, be performed by a control microprocessor orsimilar apparatus, while the functions of decimating means 520, channelinterpolating means 540 and symbol estimating means 530 may be performedby a DSP, ASIC or the like. The operations of these components iswell-known to those skilled in the art, and will not be discussed indetail herein.

Other adaptive signal processing aspects are illustrated in FIGS. 6 and7. In FIG. 6, a received signal 605 is adaptively demodulated accordingto a mobility characteristic 607. Demodulating means 610 may includeadaptive equalizing means 612 which equalizes the received signal 605according to the mobility characteristic 607 for subsequent detection indetecting means 616. The embodiment illustrated in FIG. 6 includesequalizing means 612, which includes adaptive channel tracking means 614which tracks a channel over which the signal 605 is received, based onthe mobility characteristic 607.

In FIG. 7, a plurality of signals 715 a-d are received from a pluralityof signal paths, for example, using a plurality of spatially diverseantennas 710 a-d. Signal combining means 720 combines the plurality ofsignals 715 a-d according to a mobility characteristic 717, producing acombined signal 725. Those skilled in the art will appreciate that undercertain mobility characteristics, diversity combination of signals maybe unnecessary, and that combining of diversely received signals mayconsist of selecting a single one of the signals for processing, forexample, a signal having the highest signal strength.

Those skilled in the art will appreciate that the means described withrespect to FIGS. 6 and 7 may implemented using various commonly-usedcommunications components, including special purpose hardware, softwareor firmware running on a general purpose data processing apparatus, orcombinations thereof. For example, the functions of the adaptivedemodulating means 610 and the signal combining means 720 may beperformed by a DSP, ASIC or similar circuits.

Exemplary operations for recovering information from a signal generatedin a communications medium according to the present invention areillustrated in FIG. 8 (Block 800). To recover information from a signalgenerated in a communications medium, for example, a signal generated bya base station of a cellular communications system, a mobilitycharacteristic is determined, e.g., a cell type identifier is receivedfrom the base station (Block 810). A signal generated by the basedstation is received (Block 820), and information represented by thesignal is adaptively estimated according to the received mobilitycharacteristic. For example, a channel characteristic may be selectedfor the channel over which the signal is received based on the receivedcell type identifier (Block 830), and information may be estimated fromthe received signal based on the selected channel characteristic (Block840). Those skilled in the art will appreciate that numerous variationson the above-described operations also fall within the scope of thepresent invention, including variations on the type of mobilitycharacteristic employed, the manner in which the mobility characteristicis determined, and the type of adaptive signal estimation performed. Inthe drawings and specification, there have been disclosed typicalembodiments of the invention and, although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation, the scope of the invention being set forth inthe following claims.

That which is claimed is:
 1. A communications terminal, comprising:signal receiving means for receiving a signal generated by a sourcestation of a communications system; means for receiving mobilitycharacterizing information transmitted by the communications system, thetransmitted mobility characterizing information characterizing mobilitywith respect to the source station; and adaptive signal processingmeans, responsive to the signal receiving means and to the means forreceiving mobility characterizing information, for adaptively processingthe received signal based on the received mobility characterizinginformation, and wherein the adaptive signal processing means comprises:means for adaptively estimating a channel characteristic for a channelconnecting the terminal and the source of the signal based on thereceived mobility characterizing information; and means, responsive tothe means for estimating a channel characteristic, for adaptivelyprocessing the received signal generated by the source station based onthe estimated channel characteristic.
 2. A terminal according to claim1, wherein the mobility characterizing information characterize mobilityof the terminal with respect to the source station.
 3. A terminalaccording to claim 1, wherein the adaptive signal processing meanscomprises means for adaptively demodulating the received signalgenerated by the source station based on the received mobilitycharacterizing information.
 4. A terminal according to claim 1: whereinthe signal receiving means comprises means for receiving a plurality ofsignals generated by the source station over a plurality of signalpaths; and wherein the adaptive signal processing means comprises meansfor adaptively combining the received plurality of received signalsgenerated by the source station based on the received mobilitycharacterizing information.
 5. A terminal according to claim 1, whereinthe source station comprises a cellular base station and wherein themobility characterizing information comprises mobility characterizinginformation transmitted by the cellular base station.
 6. A terminalaccording to claim 5, wherein the mobility characterizing informationcharacterizes mobility of a population of terminals typically present ina cell served by the cellular base station.
 7. A terminal according toclaim 6, wherein the mobility characterizing information comprises acell type identifier.
 8. A terminal according to claim 1, wherein themobility characterizing information characterizes mobility with respectto a cellular base station.
 9. A terminal according to claim 8, whereinthe mobility characterizing information comprises a cell typeidentifier.
 10. A terminal according to claim 1, wherein the adaptivesignal processing means comprises means for adaptively equalizing thereceived signal generated by the source station based on the receivedmobility characterizing information.
 11. A terminal according to claim10, wherein the means for adaptively equalizing comprises means foradaptively tracking a channel connecting the terminal to the sourcestation based on the received mobility characterizing information.
 12. Awireless communications terminal, comprising: signal receiving means forreceiving a signal generated by a source station of a communicationssystem; means for receiving signal propagation environmentcharacterizing information transmitted by the communications system, thetransmitted signal propagation environment information characterizing asignal propagation environment associated with the source station; andadaptive signal processing means, responsive to the signal receivingmeans and to the means for receiving signal propagation environmentcharacterizing information, for adaptively processing the receivedsignal based on the received signal propagation environmentcharacterizing information.
 13. A terminal according to claim 12,wherein the signal propagation environment characterizing informationindicates at least one of a terminal speed associated with the sourcestation and a delay spread associated with the source station.
 14. Aterminal according to claim 12, wherein the signal propagationenvironment characterizing information comprises a cell type identifierthat characterizes a signal propagation environment of a cell served bythe source station.
 15. A wireless communications terminal, comprising:a receiver that receives a signal generated by a source station of acommunications system and that receives signal propagation environmentcharacterizing information transmitted by the communications system, thereceiver including an adaptive processor that adaptively processes thereceived signal based on the received signal propagation environmentcharacterizing information, the transmitted signal propagationenvironment information characterizing a signal propagation environmentassociated with the source station.
 16. A terminal according to claim15, wherein the signal propagation environment characterizinginformation indicates at least one of a terminal speed associated withthe source station and a delay spread associated with the sourcestation.
 17. A terminal according to claim 15, wherein the signalpropagation environment characterizing information comprises a cell typeidentifier that characterizes a signal propagation environment of a cellserved by the source station.
 18. A terminal according to claim 15,wherein the receiver comprises an adaptive demodulator that adaptivelydemodulates the received signal generated by the source station based onthe received signal propagation environment characterizing information.19. A terminal according to claim 15, wherein the receiver comprises anadaptive channel estimator that estimates a channel characteristic for achannel connecting the communications station and the source stationbased on the received signal propagation environment characterizinginformation.
 20. A terminal according to claim 15, wherein the receivercomprises an adaptive equalizer that equalizes the received signalgenerated by the source station based on the received signal propagationenvironment characterizing information.
 21. A method of recoveringinformation represented by a signal generated in a communications mediumby a source station of a communications system, the method comprising:receiving the signal generated by the source station at a terminal;receiving signal propagation environment characterizing informationtransmitted by the communications system at the terminal, thetransmitted signal propagation environment characterizing informationcharacterizing a signal propagation environment associated with thesource station; and adaptively processing the received signal based onthe received signal propagation environment characterizing information.22. A method according to claim 21, wherein the signal propagationenvironment characterizing information indicates at least one of aterminal speed associated with the source station and a delay spreadassociated with the source station.
 23. A method according to claim 21,wherein the signal propagation environment characterizing informationcomprises a cell type identifier that characterizes a signal propagationenvironment of a cell served by the source station.
 24. A methodaccording to claim 21, wherein the step of adaptively processingcomprises the step of adaptively demodulating the received signal basedon the received signal propagation environment characterizinginformation.
 25. A method according to claim 21, wherein the step ofadaptively processing comprises: adaptively estimating a characteristicfor a channel connecting the source station and the terminal based onthe received signal propagation environment characterizing information;and processing the received signal generated by the first entity basedon the estimated channel characteristic.
 26. A method according to claim21, wherein the step of adaptively processing comprises the step ofadaptively equalizing the received signal based on the received signalpropagation environment characterizing information.